Coffee machine

ABSTRACT

A coffee machine, particularly an espresso machine, comprising a brewing device ( 6 ) for producing and dispensing coffee via a coffee dispensing nozzle ( 11 ), as well as a hot water boiler ( 2 ) having a fresh water supply line ( 1 ) and a hot water line ( 10 ) coming out into a brewing chamber ( 5 ) of the brewing device ( 6 ), and a control unit ( 4 ). The coffee dispensing is controllable by said control unit ( 4 ). A heating element ( 13 ) is disposed on the hot water line ( 10 ) between the hot water boiler ( 2 ) and the brewing chamber ( 5 ), by means of which heating element the water flowing from the hot water boiler ( 2 ) into the brewing chamber ( 5 ) is able to be brought to brewing temperature. The brewing temperature can thereby be maintained at a virtually constant value whereby improving the quality of the coffee dispensed.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a coffee machine for producing anddispensing coffee beverages, in particular an espresso machine, having ahousing in which are disposed at least one brewing device, a containerfor coffee beans, a grinding device connected to this container, a feedhopper for feeding the ground coffee beans into a brewing chamber of thebrewing device, a stripper for the leached ground coffee, at least onehot water boiler, comprising a fresh water supply line and a hot waterline coming out into a brewing chamber of the brewing device, a coffeedispensing nozzle and a control unit by means of which the dispensing ofcoffee is controllable.

(2) Description of Related Art

Coffee machines of this kind are known in many variations. Thus shown,for example, in GB-A-956 109 is a coffee machine of this kind. Coffeemachines for restaurant businesses, coffee machines for industrial firmsas well as coffee machines for households can be equipped according tothis system.

In order to be able to obtain as good a quality of coffee as possibledispensed from the coffee machine, the temperature of the water in thebrewing chamber which blanches the ground coffee should be at asconstant a temperature as possible (for instance 95° C.). However it isa fact that the hot water located in the hot water boiler has a highertemperature since this water cools down on the way between the hot waterboiler and the brewing chamber. This cooling down is not the same witheach dispensing of coffee, however; in particular it depends on whetherit is a first dispensing of coffee during which the lines and the valvethrough which the hot water will run as well as the brewing chamber arein a cold state, or whether these areas are warmed up owing to thepassage of the hot water for previously dispensed coffee. Depending uponthe situation, the brewing water can have too low or too high atemperature, which can affect the quality of the coffee dispensed.

An important factor which likewise affects the quality of the coffee tobe dispensed is the pressure, with which the water is pressed throughthe brewing chamber. However this pressure can be kept at a constantvalue relatively well, using known means.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is thus to improve a coffee machine suchthat the temperature of the water with which the ground coffee isblanched in the brewing chamber can be kept at a virtually constantvalue, regardless of whether a first coffee is dispensed after a breakof longer duration or whether several coffees are dispensed one afterthe other.

This object is achieved according to the invention in that in the coffeemachine between the hot water boiler and the brewing chamber a heatingelement is disposed on the hot water line, with which element the waterflowing from the hot water boiler into the brewing chamber is able to bebrought to brewing temperature, and in that the hot water line on whichthe heating element is disposed is equipped with means for adjusting theresidual water.

Achieved thereby in an advantageous way can be that the hot watertemperature in the hot water boiler is able to be kept at a lower levelthan in conventional coffee machines, the hot water to be led into thebrewing chamber for producing a coffee is brought to the desired brewingtemperature by this heating element before entering the brewing chamber,regardless of whether the hot water has cooled off more or lessintensely en route between the hot water boiler and this heatingelement. With the means for draining off the residual water, the hotwater line can be emptied after each dispensing of a coffee, wherebyprevented is that, with longer standstill of the coffee machine,residual water remaining in particular between the heating element andthe brewing chamber could cool down, and, when dispensing a coffee anew,be able to arrive in the brewing chamber in very cooled down state.

The heating element is preferably formed by a body composed of amaterial able to conduct heat, through which the hot water is able to beled, and in which a temperature-controllable heating and a temperaturesensor are integrated. Through the use of the body, a certain heatstorage in this heating element is achieved; with thetemperature-controllable heating and the temperature sensor, thequantity of heat can be supplied which is necessary to bring the waterrunning through the heating element to the desired brewing temperature.

A further preferred embodiment of the invention consists in the heatingelement being installed in the immediate vicinity of the brewing chamberafter a valve, with which the supply of warm water into the brewingchamber is controllable for producing coffee and which is disposed inthe hot water line, between the hot water boiler and the brewingchamber. A heat loss in the hot water led into the brewing chamber afterpassing through the heating element is thereby virtually avoided.

The means of draining off the residual water out of the hot water lineare preferably formed by the valve, to which valve a residual waterdrain-off line is added, whereby the hot water line running between thevalve and the brewing chamber is able to be connected to the residualwater drain-off line and emptied by switching the valve. The residualwater draining means can thereby be constructed in a simple way.

Preferably, a temperature sensor, with which the temperature of the hotwater is determinable, can be disposed in the region of the exit of thehot water line from the heating element. The temperature sensor isconnected to the control unit, whereby the heating of the heatingelement is controllable according to the measured temperature of thewater. Thereby achieved in a simple way is that the water has avirtually constant temperature.

Instead of using a temperature sensor to control the water temperature,the heating element can also be activated according to parameter values,which parameter values are storable in memory means provided in thecontrol unit. The temperature of the water able to be led into thebrewing chamber can thereby be kept constant in an advantageous waywithout additional probes or sensors being necessary.

Embodiments of the present invention will be explained more closely inthe following, by way of example, with reference to the attacheddrawing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Shown are:

FIG. 1, is a schematic representation, the arrangement of the heatingelement in a coffee machine as a first embodiment example;

FIG. 2, is a schematic representation, the arrangement of a heatingelement in a coffee machine according to a second embodiment example;and

FIG. 3, is a graphic representation, the course of the temperature ofthe water running into the brewing chamber in a conventional coffeemachine and in a coffee machine according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen from the schematic representation according to FIG. 1, ofthe essential elements of a coffee machine according to the invention,which elements are accommodated in a housing (not shown), fresh water isled via a fresh water supply line 1 into a hot water boiler 2 of thecoffee machine. This can take place from a fresh water container or froma fresh water supply network (not shown) by means of a pump forinstance. The water is heated in the hot water boiler by means of aheater 3, which is connected to a control unit 4. Via a temperaturesensor 5, likewise connected to the control unit 4, the heater 3 isactivated in such a way that the water in the hot water boiler 2 is keptat an approximately constant temperature. This temperature cancorrespond approximately to the desired brewing temperature of thewater. The water in the hot water boiler is under pressure, for exampleat about 11 bar.

If coffee is dispensed, coffee beans, contained in a container 26, aresupplied from this container 26 to a coffee mill 25 in a known way.These coffee beans are ground. Via a feed hopper 27, the freshly groundcoffee is filled into the brewing chamber 5 of the brewing device 6,which is opened in the upper region by the piston 8 being driven out ofthe brewing chamber 5 and which is closed in the lower region by thepiston 7. The brewing chamber 5 is then closed by the piston 8.Installed in the line coming out of the hot water boiler 2 is a valve 9,which is brought into the position in which the hot water from theboiler 2 is able to arrive in the hot water line 10. This hot water line10 leads the hot water via the piston 7 into the brewing chamber 5,where the ground coffee is blanched. By means of the piston 8 the brewedcoffee reaches the coffee dispensing nozzle 11 and from there the coffeecup 12.

Just before the brewing chamber 5 the hot water line 10 passes through aheating element 13. This heating element 13 is formed by a body 14 madeup of a material capable of heat conduction, for example of aluminum(aluminium). Integrated into this body 14 is a temperature-controllableheating 15 and a temperature sensor 16, which are connected to thecontrol unit 4. Furthermore disposed in the region of the exit of thehot water line 10 out of the heating element 13 is a temperature sensor17, with which the temperature of the hot water is able to bedetermined. When dispensing a coffee, the heating 15 of the heatingelement 13 is activated by the control unit 4, and brings the body 14quickly to a temperature corresponding to the brewing temperature ofabout 95° C. When the water flows through the hot water line 10, itstemperature is measured by the temperature sensor 16; on the basis ofthis measured temperature the heating element 13 is controlled by thecontrol unit 4 in such a way that the brewing temperature of the waterwhich is led into the brewing chamber 5 remains virtually constant.

When the required amount of water needed for the coffee dispensing haspassed through the valve 9, which is determined in a known way through aflow meter, the control unit 4 brings about a closing of the valve 9, inaddition to the turning off of the pump. The valve 9 is then switched insuch a way that the hot water line 10 is connected to a residual waterdrain-off line 18, whereby the water located in the hot water line 10 isdrained in a known way into a residual water container (not shown).Prevented thereby is that water remains in the hot water line 10 and cancool down during longer non-use of the coffee machine, in particular inthe region of the hot water line 10 situated between the heating element13 and the brewing chamber 5. If the hot water line 10 were not to beemptied, then during the next dispensing of coffee, this cooled-downwater would first come into contact with the ground coffee to beblanched, whereby the quality of the coffee dispensed could be affected.

After dispensing of a coffee, the brewing chamber 5 is opened in a knownway in that the piston 8 is driven out of the brewing chamber 5. Thepiston 7 subsequently pushes the leached ground coffee to the edge ofthe brewing chamber 5; these are then led away in a known way by astripper 28 and are brought into a collecting container (not shown).

Ensured with this device is that the water arriving in the brewingchamber 5 has practically always the same brewing temperature,regardless of whether a normal coffee with a larger amount of water oran espresso with a relatively small amount of water is dispensed, andalso regardless of whether it is the first coffee or espresso coffee ineach case which has been dispensed after a longer interruption of thecoffee machine or whether several coffees have been dispensed alreadybeforehand. A consistently good quality of the coffee dispensed isthereby ensured.

Visible in a schematic representation in FIG. 2 is a practicallyidentical coffee machine as in FIG. 1. In this figure the elements havebeen given the same reference numerals as the corresponding elementsaccording to FIG. 1. The only difference is that the temperature sensor17 (FIG. 1) has been omitted in this embodiment example.

The dispensing of coffee takes place in an identical manner as has beendescribed with respect to FIG. 1, whereby the heating 15 is activated bythe control unit 4 on the basis of parameter values, which parametervalues are storable in memory means 29 in the control unit 4 in a knownway. These parameter values are, on the one hand, empirical values as tohow the elements passed through by the hot water cool down over time,and how the heating takes place depending upon the amount of water ledthrough. Further parameter values are whether a normal coffee or anespresso coffee is dispensed, what time has passed by since the lastdispensing of a coffee or an espresso coffee until the dispensing againof a coffee or espresso coffee. Based on these parameter values thecontrol unit calculates what quantity of heat is to be delivered by theheating element 14 to the water passing through this heating element 14,and controls accordingly the heating 15 of the heating element 14. Theparameter values which are empirical values have been determined inlong-term tests on a coffee machine equipped with the necessarymeasuring means.

With the coffee machines designed according to the invention it becomespossible for the brewing water arriving in the brewing chamber, withwhich the ground coffee is blanched and the coffee thereby produced, tohave a substantially constant temperature, whereby the quality of thecoffee is able to be improved.

From the time-temperature diagram, shown in FIG. 3, the curve 19 showsthe temperature course of the brewing water when entering the brewingchamber of a conventional machine, while curve 20 shows the temperaturecourse of a coffee machine designed according to the invention. With theconventional machine (curve 19), the water led first into the brewingchamber has too low a temperature since the elements in the hot waterline first have to be warmed up. In the course of the brewing processthe temperature rises and exceeds the optimal brewing temperature of 95°C., since the water in the hot water boiler has a temperature higherthan this 95° C., in order to be able to reach the brewing temperatureat all.

With the coffee machine according to the invention, the water is heatedby the heating element to 95° C. before entering the brewing chamber,and is kept constant at this temperature, as can be learned from thecurve 20. With the conventional coffee machine, therefore, a firstportion of the coffee is brewed at too low a temperature, shown by thehatched area 21, whereas the last portion of the coffee is brewed at toohigh a temperature, shown by the hatched area 22. If after a certaintime, indicated by the double arrow 23, a new coffee is dispensed ineach case, the temperature differences of the brewing water havedecreased in the conventional machine since the elements passed throughby the hot water have not yet cooled down all too much. Nevertheless onestill obtains a portion of coffee brewed too cold and a portion ofcoffee brewed too hot, as is indicated by the areas 21′ and 22′.

With the coffee machine according to the invention, on the other hand,the optimal brewing temperature is maintained.

1. Coffee machine for producing and dispensing coffee beverages, inparticular an espresso machine, which has a housing in which aredisposed at least one brewing device (6), a container (26) for coffeebeans, a grinding device (25) connected to this container (26), a feedhopper (26) for feeding the ground coffee into a brewing chamber (5) ofthe brewing device (6), a stripper (28) for the leached ground coffee,at least one hot water boiler (2) having a fresh water supply line (1)and a hot water line (10) coming out into the brewing chamber (5) of thebrewing device (6), a coffee dispensing nozzle (11) and a control unit(4) by means of which the dispensing of coffee is controllable,characterized in that between the hot water boiler (2) and the brewingchamber (5) a heating element (13) is disposed on the hot water line(10), with which element the water flowing from the hot water boiler (2)into the brewing chamber (5) is able to be brought to brewingtemperature, and in that the hot water line (10), on which the heatingelement (13) is disposed, is equipped with means (9, 18) for drainingoff the residual water, said heating element (13) comprising a body (14)composed of a material able to conduct heat, through which the hot wateris able to be led, and in which a temperature-controllable heating (15)and a temperature sensor (16) are integrated, said heating element (13)being installed in the immediate vicinity of the brewing chamber (5)after a valve (9), with which the supply of warm water into the brewingchamber (5) is controllable for producing coffee and which is disposedin the hot water line (10), between the hot water boiler (2) and thebrewing chamber (5).
 2. Coffee machine according to one of the claim 1,characterized in that the means of draining off the residual water inthe hot water line (10) are formed by the valve (9), to which valve aresidual water drain-off line (18) is added, whereby the hot water line(10) running between the valve (9) and the brewing chamber (5) is ableto be connected to the residual water drain-off line (18) and emptied byswitching the valve (9).
 3. Coffee machine according to one of the claim1, characterized in that a temperature sensor (17), with which thetemperature of the hot water is determinable, is disposed in the regionof the exit of the hot water line (10) from the heating element (13). 4.Coffee machine according to claim 3, characterized in that thetemperature sensor (17) is connected to the control unit (4), by meansof which the heating (15) of the heating element (13) is controllableaccording to the temperature measured.
 5. Coffee machine according toone of the claim 1, characterized in that the heating (15) of theheating element (13) is able to be activated according to parametervalues, which parameter values are storable in memory means (29)provided in the control unit (4).